This invention relates to an end brush formed of a bundle of thermoplastic fibers, in which one end of the bundle of fibers is formed of solidified fiber material. This type of brush is useful in an apparatus for cleaning the teeth, wherein rotation is imparted to the brush.
It is known to form an end brush from a bundle of thermoplastic fibers in which an end of the fiber bundle is subjected to a heating step so as to melt the fiber ends, and to thereafter cool the melted fiber material so as to provide a substantially rigid base to the end brush.
Application Ser. No. 07/283,089, filed Dec. 12, 1988 discloses an end brush of this type, and also an apparatus for manufacture thereof. In the noted application, the resultant end brush has a base formed of solidified fiber material, and a passage formed in the base. The passage has splined walls formed by insertion of a heated male splined pin into the fiber ends. The heated pin melts the fibers as it is inserted into the fiber bundle. After the heated pin is withdrawn from the fiber bundle and the melted fiber material has cooled, the melted fiber material forms a substantially rigid base for the end brush. The brush is then placed onto a dental unit which includes a rotating driveshaft having a splined configuration similar to that of the passage formed in the base of the end brush, for imparting rotation thereto. An apparatus with which such a brush is useful is disclosed in U.S. Pat. No. 4,827,552 issued May 9, 1989.
While the end brush as described above has proven satisfactory in construction and operation, it has been found that cost savings and quality enhancements are attainable over the known brush and apparatus. The present invention is directed to this end.
In accordance with the invention, a brush assembly, such as for use in a dental unit, comprises a brush formed of a bundle of fibers extending from a base. The base is formed of solidified fiber material and includes an outwardly extending dimensionally defined projection. Drive means is provided for imparting rotation to the brush, and mounting means is associated with the drive means for securing the brush thereto. The mounting means includes a recess adapted to receive the outwardly extending projection of the base of the brush. Means is provided for securing the outwardly extending projection of the base of the brush within the recess. The projection is formed of solidified fiber material, and preferably includes a transversely enlarged portion. The securing means comprises an area associated with the recess for receiving the transversely enlarged portion, so that the brush provides a snap-fit onto the mounting means by a push-on force mating the projection with the recess.
With this construction, the driveshaft in the known tooth cleaning apparatus can be eliminated, and is replaced by mating of the projection with the recess provided in the mounting means. The recess is preferably formed in an outwardly facing surface of a gear, which is adapted to be rotatably driven by the dental unit drive system, for imparting rotation to the brush. In a preferred embodiment, positive engagement means is provided for preventing slippage of the brush relative to the gear during operation. The positive engagement means may include a rib formed on the base of the brush protruding laterally from the projection and, means associated with a wall of the recess for engaging the protrusion so as to prevent slippage.
The invention also contemplates an end brush constructed substantially in accordance with the above description.
Also contemplated by the invention is a method of forming an end brush. The method includes providing a bundle of generally parallel fibers formed of thermoplastic material, and liquefying the fiber ends at an end of the bundle so as to unite the fibers. The liquefied fiber material is formed to a shape providing an outer portion lying in a first plane substantially perpendicular to the fibers, and an inner portion extending below the outer portion so as to form a projection. The liquefied fiber material is then solidified, so as to form a rigid base. In a preferred embodiment, the fiber ends are liquefied by moving a heated element into engagement with the fiber ends so as to melt the fibers. Thereafter, the melted fiber material is cooled so as to solidify the material and form the base. The liquefied fiber material is formed by providing the heated element with an upper outer surface and in inner surface disposed therebelow. Movement of the heated element into contact with the fiber ends melts the fiber material adjacent the fiber ends so that the melted fiber material conforms to the shape of the heated element. The melted fiber material adjacent the upper outer surface forms the outer portion, and the melted fiber material adjacent the inner surface forms the inner portion projecting below the outer portion. In a preferred embodiment, the heated element comprises an outer sleeve with a movable insert. Upward movement of the pin after the melted fiber material as solidified knocks the brush off of the heated element, preparing the heated element for subsequent usage in forming another brush.
The invention finally contemplates an apparatus for forming an end brush from a bundle of thermoplastic fibers. The apparatus comprises means for receiving the bundle of fibers and selectively clamping the bundle adjacent an end thereof. A movable element is movable into contact with the end of the fiber bundle. Heating means is provided for heating the movable element prior to contact with the fiber ends, so that the fiber ends are liquidified when the movable element is brought into contact therewith. The movable element is provided with means for forming the liquefied fiber material to a shape providing an outer portion lying in a first plane substantially perpendicular to the fibers, and an inner portion extending below the outer portion so as to form a projection. The apparatus includes cooling means for solidifying the melted fiber material so as to form a rigid base. As described previously, the movable element preferably comprises a tubular sleeve, with an insert or pin disposed within the sleeve. The upper end of the pin is disposed below the upper end of the sleeve when the movable element is moved into contact with the fiber ends. The forming means thus comprises the upper end of the sleeve providing the outer portion, and the cavity formed by upper end of the pin and the inner wall of the sleeve providing the inner portion. The inner wall of the sleeve is preferably provided with a circumferential groove or indentation disposed above the upper end of the pin. In this manner, when the movable element is brought into contact with the fiber ends, melted fiber material flows into the indentation to provide an area of enlarged transverse dimension to the projecting portion of the brush base.